SELECT 
    'ALTER TABLE "' || TABLE_NAME || '" MODIFY "' || COLUMN_NAME || '" DECIMAL(19,3);' AS ALTER_SQL
FROM 
    USER_TAB_COLUMNS
WHERE 
    DATA_TYPE = 'DOUBLE';

SELECT ALTER_SQL FROM 
(

SELECT 
     DISTINCT  ('ALTER TABLE "' || TABLE_NAME || '" MODIFY "' || COLUMN_NAME || '" DECIMAL(19,3);') AS ALTER_SQL,TABLE_NAME,COLUMN_NAME
FROM 
    USER_TAB_COLUMNS
   WHERE DATA_TYPE LIKE '%REAL%' 
   OR DATA_TYPE LIKE '%FLOAT%' 
   OR DATA_TYPE LIKE '%DOUBLE%' AND TABLE_NAME LIKE 'Tbl%'
   
   ) z ORDER BY  TABLE_NAME,COLUMN_NAME